Ryanair has missed the deadline to respond the pilots’ demands for improved employment terms, raising the prospect of further disruption of flights.

Ryanair pilots are set to write to Michael O’Leary, chief executive of the company, branding him a “disgrace” over the way in which the fallout from rota issues were handled. These problems have forced the carrier to cancel up to 50 flights a day.

This escalation comes after over 30 pilots of Ryanair’s European bases gave the Irish carrier until 10am on Friday to address their concerns.

The group of pilots, who have hired professional negotiators, sent Ryanair a letter, detailing demands, including new employment contracts to be negotiated by 1 January, 2018 and common working conditions throughout the carrier’s network.

Currently, many Ryanair pilots are employed via temporary agency contracts, which contributes to the airline being able to keep costs down.

Signed by pilots based at 32 European airports, the letter said that agreeing to change this model would “help keep our planes in the air” and make sure that “cancellations will be minimised”.

However, two pilots said that the company has ignored the ultimatum, allowing the deadline to pass.

An early draft of a second letter due to be sent to Ryanair today, criticising O’Leary’s handling of the dispute has been seen by The Guardian.

“As a pilot group we regret that you are not willing to solve the problems Ryanair is facing now,” the letter reads.

“We offered our help, however you prefer to cancel flights and leave the passengers out in the cold. We do not understand why Ryanair management sees us as the enemy when we are actually colleagues.”

The letter, which is being circulated among Ryanair’s European bases, also criticises O’Leary for comments made at this week’s annual general meeting, in which he accused pilots of being “precious” and questioned the difficulty of their job.

“Management should be ashamed of themselves,” pilots said. “What you say at press conferences is a disgrace to all employees and contractors. Ryanair has been doing well for so many years and that is all because of us.”

One ex-Ryanair pilot said many of his colleagues were unimpressed with the company’s offer of a tax-free bonus of up to £12,000, if they fly during their time off, to avoid further cancellations during the rest of the year.

“[O’Leary] wants to buy himself into January and do it as cheap as possible, the way he always does,” he said.

“Of course €10,000 is not nothing. But this is an airline that’s planning to report close to €1.5bn profit. He wants to buy himself out of this crisis for pennies.”